The present invention relates to rotary indexing mechanisms for rotating a shaft or shaft-connected member through a defined angular increment and, more particularly, to a rotary indexing mechanism that is less complicated than prior devices and which provides precise angular increments and end-of-movement positioning.
Various types of mechanical, electro-mechanical, and electronic rotary indexing mechanisms are known for providing incremental rotation of a shaft through a selected angular increment. Mechanical devices include pawl and rachet assemblies in which a first pawl rotates a rachet and a second pawl maintains the rotated rachet at its end-of-movement position and detent mechanisms in which a resiliently biased detent member engages the rotated member at selected detent positions. Electrical actuators, typically in the form of solenoids and other electro-magnetic devices, have been adapted to drive mechanical mechanisms to provide increased control. Lastly, electronic rotary indexing devices have used drive motors, usually of the stepper motor type, and shaft position sensors to provide a wide range of control including control of the size of the rotary increment and the precise end-of-movement location of the rotated member.
While prior rotary indexing mechanisms and devices have been satisfactory, many of the mechanical and electro-mechanical mechanisms do not provide for the precise end-of-movement positioning of the rotated member or an ability to adjust the end-of-movement position. Additionally, some prior devices apply a non-uniform force to the rotated member and cause undesirable variations in the motion of the rotated member as it is incremented. Electronically controlled indexing motors and their related control circuitry do provide precise incrementing and end-of-movement position control but are oftentimes too expensive for many applications.